where \(\theta _t\)  denotes the parameters of blue\(Q\)  of Eq. (REF ) and \(\theta ^{-}_t\)  is a periodic copy of \(\theta _t\) .
It is worth noting here that following the suggestion in [1]} a separate network is used to determine the TD-Target. This target DQN is initialised with the same parameters as the main DQN (the so-called policy DQN), but has its parameters updated every \(k\)  iterations.
blueThat is, the expected \(Q\)  values of the target DQN are fixed and every \(k\)  iterations the parameters of the policy DQN are copied to the target DQN.
